Compounds exhibiting intense light absorbance in a range of 550 to 620 nm, particularly compounds having a maximum absorbance wavelength (λmax) at 550 to 620 nm, are used as optical recording materials to form an optical recording layer of optical recording media such as DVD-R.
As the optical recording materials, there are many reports with indolium compounds having an indole ring since they give merits of high sensitivity and good response to increase in recording speed. For example, Patent Documents 1 to 6 report styrylindolium compounds. Patent Document 7 reports a low-temperature decomposable cyanine compound in which a benzyl group is introduced into the 3-position of indole ring. Low-temperature decomposable compounds readily form recording segments (pits) in optical recording layers and are considered to fit for high-speed recording media.                Patent Document 1: Japanese Patent Laid-open Publication No. H11-34489        Patent Document 2: Japanese Patent Laid-open Publication No. H11-170695        Patent Document 3: Japanese Patent Laid-open Publication No. 2001-342366        Patent Document 4: Japanese Patent Laid-open Publication No. 2002-206061        Patent Document 5: Japanese Patent Laid-open Publication No. 2003-313447        Patent Document 6: Japanese Patent Laid-open Publication No. 2003-321450        Patent Document 7: Japanese Patent Laid-open Publication No. 2003-231359        